#include <iostream>
#include <cctype>
#include "stack.h"

int main()
{
    using namespace std;
    Stack st;
    char ch;
    unsigned long po;
    cout << "Please enter A to add a purchase order, \n";
    cout << "P to process a PO, or Q to quit.\n";
    while(cin >> ch && toupper(ch) != 'Q')
    {
        while(cin.get() != '\n') continue;
        if(!isalpha(ch))
        {
            cout << '\a';
            continue;
        }
        switch(ch)
        {
        case 'A':
        case 'a':
            cout << "Enter a PO number to add: ";
            cin >> po;
            if(st.isfull())
                cout << "stack already full\n";
            else
                st.push(po);
            break;
        case 'P':
        case 'p':
            if(st.isempty())
                cout << "stack already empty\n";
            else
            {
                st.pop(po);
                cout << "PO #" << po << " popped\n";
            }
            break;
        }
        cout << "Please enter A to add a purchase order,\n";
        cout << "P to process a PO, or Q to quit.\n";
    }

    cout << "Bye.\n";
    return 0;
}
